The invention relates generally to disc drives and, more particularly, to a disc drive assembly having a damped protective cover to improve disc drive acoustics.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces. The actuator thus allows the head to move back and forth in an accurate fashion between an inner radius and an outer radius of the discs.
Much of the electronics that are essential to the disc drive""s operation is mounted on the disc drive""s printed circuit board assembly (xe2x80x9cPCBAxe2x80x9d). The PCBA includes electrical components that manage the operations of the disc drive. For example, the PCBA includes electrical components that control the speed of the spindle and position of the actuator arms over the discs. Similarly, the PCBA also includes electrical components that interface with the computer""s processor.
A protective cover may be attached to the disc drive assembly to protect the PCBA from exposure to electrostatic discharge. These protective covers make installation easier and serve to minimize handling damage. However, when a protective cover over the PCBA is used, the protective cover can vibrate and increase the acoustic emissions from the disc drive. As acoustics standards continue to tighten, the overall acoustical emissions from disc drive assemblies must also be reduced. Accordingly, there is a need for improving the acoustic emissions from disc drive assemblies which include a PCBA protective cover.
The present invention provides solutions to the above and other problems. The disc drive in accordance with the present invention incorporates a damped PCBA protective cover for reducing acoustic emissions in a disc drive. The disc drive assembly comprises a base, a circuit board mounted to the base and a protective circuit board cover fastened to the base and extending over the circuit board. The circuit board is thus disposed between the base and the cover. Furthermore, a constrain layer is affixed to the cover. This constrain layer preferably has a stiffening member and a damping member sandwiched together, although the cover itself may constitute the constrain layer if the material from which the cover is made has the desired damping characteristics. Preferably, the damping member is disposed between the cover and the stiffening member. The stiffening member and the damping member together cooperate to reduce the vibrational and acoustical energy produced by the cover during operation of the disc drive.
The protective cover is a generally flat plate having a first side facing away from the circuit board and a second side facing the circuit board. The constrain layer may be affixed to and sized and configured to correspond to the surface shape of the first side of the cover facing away from the circuit board in one preferred embodiment of the present invention. In an alternative preferred embodiment, the constrain layer may be affixed to and sized and configured to correspond to the surface of the second side of the cover, facing the circuit board. In this alternative embodiment, the constrain layer may include recessed areas that correspond to the location of electrical components mounted on the circuit board.